The present invention relates to a conveying apparatus for conveying a conveyance object by a rotation of a conveyor roller.
In a conventional image forming apparatus, such as an inkjet printer, a conveyor roller is used to convey a recording sheet or the like as a recording medium. Such a conveyor roller is equipped with a rotary encoder to detect a rotation angle of the conveyor roller such that a feed amount and a conveyance position of the recording medium can be controlled in accordance with the rotation of the conveyor roller.
The rotary encoder usually includes a code wheel (a disk) and an optical sensor. The code wheel having slits formed at approximately equal intervals along a circumferential direction is fixed to a rotation shaft of the conveyor roller. The optical sensor detects passage of the slits caused by a rotation of the code wheel.
According to the above configuration, a pulse signal is output from the rotary encoder by each specified rotation angle of the conveyor roller. By measuring a generation interval (time interval) of the pulse signals, a rotation speed of the conveyor roller can be detected. By counting a number of the pulse signals, a rotation angle of the conveyor roller can be determined.
To improve a resolution of a conveyance amount which is controllable by the pulse signals from the rotary encoder, a pulse number to be output from the rotary encoder per rotation of the conveyor roller should be increased. This may be achieved by reducing slit intervals of the code wheel or increasing a diameter of the code wheel, thereby to increase a number of the slits to be formed in the code wheel.